The Diatomaceæ of Philadelphia and Vicinity

by Charles S. Boyer

AMPHORA ROBUSTA GREG.

Frustule elliptical, truncate; valve lunate, with straight ventral margin; median line biarcuate; ventral side with coarse, radiate striæ, 6 in 10 µ, on both sides of the median line.

Along the coast.

Pl. [15], Fig. 1.

AMPHORA PROTEUS GREG.

Frustule elliptical, truncate; valve lunate, with straight ventral margin; median line biarcuate; no central area. Striæ on the dorsal side not interrupted, 9 in 10 µ. Ventral side striate toward the ends.

Differs from A. robusta chiefly in size and coarseness of puncta. Extremely variable in size.

Common along the coast.

Pl. [15], Figs. 5, 6, and 19.

AMPHORA OVALIS (BRÉB.) KUETZ.